On OSX 10.8.2 on my 2011 MBA I was starting a new project.
In that empty folder, which I already had open in ST3 I, installed express via npm in the command line - all of a sudden my laptop just froze up.
What seems to happen is this: cl.ly/0O133c3R2g3R - the indexing service threads startup - however very quickly the laptop starts to freeze up - you can see this quite quickly - express should not take that long to install, and stopping the screencast takes quite a few seconds. However there is no indication in ST3 that it is indexing anything, you can only see this via the activity monitor.
However, even after killing ST3 I noticed that the threads, not only do they continue to run but actually continue to go up (again, recorded here cl.ly/0Y1K3X0R1f3o).
I'd call this a pretty serious bug (my MBA fan went into overtime and got very hot)